Many of the definitive characteristics of a structure are perceived by a viewer or investigative system by properties of its surface. While the surface characteristics may be entirely different from characteristics of the underlying structure, still they at least suggest to the observer significant information about the structure itself.
For example, a coat of paint on the chassis of a vehicle says something about the shape and color of the coat of paint on the vehicle, but it says nothing about the metal skin on which it is laid, except for its outer shape and color assuming that the paint is a uniform layer. Similarly it says nothing about an engine or anything else inside of it or inside an overlaying or shrouding skin. Thus, the characteristics of a surface which is directly viewed by the observer convey all of the information available to the observer. Changing these characteristics can change the observer's perception of the structure itself.
For example, in visible light, color patterns in a coat of paint may be of considerable interest. National emblems, cautionary displays, distracting or misleading images, and colors that do or do not contrast with the background are examples. Some colors may be intended to be glaringly obvious, while others are preferred to fade into the background. The art of color camouflage exemplifies one field of presenting a colored surface that is hopefully hidden in plain sight.
The above relates to reactions to visible light which light is emitted by, or which is reflected from the surface. This is only one example of means to perceive a structure. Other means which are pertinent to this invention are responses to frequencies outside of the visible spectrum, for example infrared and radar frequencies. For these, observation devices vary from reception of frequencies emitted or which are reflected by the surface itself, namely its infrared emission, or received (or modified) reflection of radar frequencies originated by the observing device which are reflected by the surface.
It is an object of this invention adaptively to change significant properties of the surface of a structure, by altering the emissive properties of the surface itself, or by altering its reflective properties. In both of these circumstances an observing device or person will be convinced to perceive pertinent properties that are not necessarily those of the underlying structure.
Reduced to absurdity, a structure may be camouflaged by repainting it, or by painting over indicia, for example. But then this arrangement remains until a next coat of paint is applied. Desert vehicles are painted once. If they are sent to the Arctic, they may be painted another color. But when they are in one place, their perceived color pattern is established and does not change.
In contrast, this invention proposes to alter surface properties literally on demand, between at least two different conditions. In this specification, the “perceived surface” is the interface with the atmosphere which is sensed by an observer. Its properties are determined by its immediate substrate. For example, the perceived surface of a coat of paint possesses properties determined by its substrate paint. A coating that does not alter the characteristics being observed is not regarded as the perceived surface for purposes of this invention.
This invention utilizes the effect of temperature of the perceived surface to alter the observed characteristics. For adaptive purposes, if temperature is the sensed property, the alternating property is the temperature itself. If color or some other reflected observable property is to be sensed, then a temperature-responsive substance is used for the exposed surface, with a substrate whose temperature can be changed. Of course, the surface may itself be the boundary of a substrate of the same material, for example a coat of paint. Thermochromic films or layers for change of colors, and embedded radar absorbing particles whose size changes with temperature to vary reflection or adsorption of radar frequencies are examples.
The change of temperature is achieved by the use of the well-known Peltier effect, in which a lower temperature is created on one side of a semi-conducting array or layer, and an elevated temperature on the opposite side. This essentially is the transfer of caloric heat to or from the first surface, (usually the exposed surface) to an underlying substrate or structure. The temperature of the exposed surface can thereby be changed, either increased or decreased, by current applied to the device, and the direction of the effect. To increase the effect, one merely increases the current density. Thus, by the mere exertion of an electrical current, the temperature, and with it the perception of a surface, can adaptively be adjusted and changed. Such devices are frequently used as “thermoelectric coolers” (TEC).
With the change in temperature of the exposed surface, its visible or emission properties can be changed, resulting in confusion of the observer.